Ch. 18 The Endocrine System Flashcards
(154 cards)
1
Q
What two systems coordinate the functions of all body systems?
A
the nervous and endocrine systems
1
Q
The nervous system controls body actions through…
A
nerve impulses
2
Q
The endocrine system controls body activities by…
A
releasing mediator molecules called hormones
3
Q
Endocrinology
A
science concerned with the structure and function of the endocrine glands and the diagnosis and treatment of endocrine disorders
4
Q
True or False: parts of the nervous system stimulate or inhibit the release of hormones
A
true
5
Q
Hormones may promote or inhibit the generation of _____ _______
A
nerve impulses
6
Q
Two kinds of glands in the body
A
exocrine and endocrine
7
Q
Exocrine glands
A
secrete their products into ducts and the ducts carry the secretions to the target site
8
Q
Endocrine glands
A
secrete their products (hormones) into the interstitial fluid surrounding the secretory cells from which they diffuse into capillaries to be carried away by blood
9
Q
Endocrine glands include:
A
-pituitary
-thyroid
-parathyroid
-adrenal
-pineal
10
Q
When do hormones have powerful effects?
A
when present in very low concentrations
11
Q
Although hormones travel in blood throughout the body, what do they only affect?
A
specific target cells
12
Q
What do target cells have for hormones to bind to?
A
specific protein or glycoprotein receptors
13
Q
Down-regulation
A
the decrease in the number of receptors when a hormone is present in excess
14
Q
Up-regulation
A
an increase in the number of receptors when a hormone is deficient
15
Q
Synthetic hormones
A
available as drugs that block the receptors for particular naturally occurring hormones
16
Q
Circulating hormones or endocrines
A
hormones that travel in blood and act on distant target cells
17
Q
Local hormones
A
hormones that act locally without first entering the bloodstream
18
Q
Paracrines
A
those that act on neighboring cells
19
Q
Autocrines
A
those that act on the same cell that secreted them
20
Q
Lipid-soluble hormones
A
steroids, thyroid hormones, and nitric oxide, which acts as local hormone
21
Q
Water-soluble hormones
A
the amines; peptides, proteins, and glycoproteins; and eicosanoids
22
Q
How do water-soluble hormones circulate?
A
in the plasma in a free, unattached form
23
Q
How do lipid-soluble hormones bind?
A
to transport proteins to be carried in blood
24
What do transport proteins do?
they improve the transportability of lipid-soluble hormones by making them temporarily water-soluble, retard passage of the small hormone molecules through the kidney filter thus slowing the rate of hormone loss in urine, and provide a ready reserve of hormone already present in blood
25
What do digestive enzymes destroy?
protein and peptide hormones such as insulin
26
What determines the response to a hormone?
it depends on both the hormone and target cell
27
Action of lipid-soluble hormone
1. Lipid-soluble hormones bind to and activate receptors within cells
2. The activated receptors then alter gene expression which results in the formation of new proteins
3. The new proteins alter the cells activity and result in the physiological responses of those hormones
28
Action of water-soluble hormones
1. water-soluble hormones alter cell functions by activating plasma membrane receptors, which set off a cascade of events inside the cell
2. a typical mechanism of action of a water-soluble hormone using cyclic AMP as the second messenger
3. since hormones that bond to plasma membrane receptors initiate a series of events, they can induce their effects at very low concentrations
4. the cholera toxin modifies G-proteins in epithelial cells lining the intestine so they become locked in an activated state which results in the massive fluid loss this toxin causes
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First messenger
the water-soluble hormone that binds to the cell membrane receptor
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Second messenger
released inside the cell where hormone-stimulated response takes place
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What determines the responsiveness of a target cell to a hormone?
the hormone's concentration, the abundance of the target cell's hormone receptors, and influences exerted by other hormones
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The three hormonal interactions
permissive effect, synergetic effect, and the antagonist effect
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How are most hormones released?
in short bursts, with little or no release between bursts
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What does the regulation of hormone secretion do?
it normally maintains homeostasis and prevents overproduction or underproduction of a particular hormone
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What controls hormone secretion?
signals from the nervous system, chemical changes in the blood, and other hormones
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_______ feedback systems regulate hormonal secretions
negative
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What is the major integrating link between the nervous and endocrine systems?
the hypothalamus
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What do the hypothalamus and the pituitary gland regulate?
virtually all aspects of growth, development, metabolism, and homeostasis
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Where is the pituitary gland located?
in the sella turcica of the sphenoid bone
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What is the pituitary gland differentiated into?
the anterior pituitary (adenohypophysis), the posterior pituitary (neurohypophysis), and pars intermedia
41
What controls the hormones of the anterior pituitary?
releasing or inhibiting hormones produced by the hypothalamus
42
Where is the blood supply to the anterior pituitary from?
the superior hypophyseal arteries
43
Hormones of the anterior pituitary and the cells that produce them:
1. human growth hormone (hGH) is secreted by somatotrophs
2. thyroid-stimulating hormone (TSH) is secreted by thyrotrophs
3. follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are secreted by gonadotrophs
4. prolactin (PRL) is secreted by lactotrophs
5. adrenocorticotrophic hormone (ACTH) and melanocyte-stimulating hormone (MSH) are secreted by corticotrophs
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What regulates the secretion of the anterior pituitary gland hormones?
hypothalamic regulating hormones and by negative feedback mechanisms
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What is the most plentiful anterior pituitary hormone?
Human growth hormone (hGH)
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What does hGH do?
it acts indirectly on tissues by promoting the synthesis and secretion of small protein hormones called insulinlike growth factors (IGFs)
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What do insulinlike growth factors do?
stimulate general body growth and regulate various aspects of metabolism
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What is a symptom of excess hGH?
hyperglycemia
49
Thyroid-stimulating hormone (TSH)
regulated thyroid gland activities and is controlled by TFH (thyrotropin-releasing hormone)
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Follicle-stimulating hormone (FSH)
-in females, initiates follicle development and secretion of estrogens in the ovaries
-in males, FSH stimulates sperm production in the testes
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Luteinizing Hormone (LH)
-in females, LH stimulates estrogen secretion by ovarian cells to result in ovulation and stimulated formation of corpus luteum and secretion of progesterone
-in males, LH stimulates the interstitial cells of the testes to secrete testosterone
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Prolactin (PRL)
initiates and maintains milk secretion by the mammary glands
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Adrenocorticotrophic hormone (ACTH)
controls the production and secretion of hormones called glucocorticoids by the cortex of the adrenal gland
54
Melanocyte-stimulating hormone (MSH)
increases skin pigmentation although its exact role in humans is unknown
55
Posterior pituitary gland (neurohypophysis)
stores and releases two hormones
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Where is the neural connection between the hypothalamus and the neurohypophysis?
via the hypothalamohypophyseal tract
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What hormones are made by the hypothalamus and stored in the posterior pituitaty?
oxytocin (OT) and antidiuretic hormone (ADH)
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Oxytocin
stimulates contraction of the uterus and ejection of milk from the breasts
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What stimulates oxytocin release?
nursing a baby after delivery
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Antidiuretic hormone
stimulates water reabsorption by the kidneys and arteriolar constriction
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Effect of ADH
to decrease urine volume and conserve body water
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What is ADH controlled by?
primarily by osmotic pressure of the blood
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Where is the thyroid gland located?
just below the larynx and has right and left lateral lobes
64
How are thyroid hormones synthesized?
from iodine and tyrosine within a large glycoprotein molecule called thyroglobulin
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How are thyroid hormones transported?
in the blood by plasma proteins, mostly thyroxine-binding globulin
66
Formation, storage, and release steps of thyroid hormones
iodide trapping, synthesis of thyroglobulin, oxidation of iodide, iodination of tyrosine, coupling of T1 and T2, pinocytosis and digestion of colloid, secretion of thyroid hormones, and transport in blood
67
What do thyroid hormones regulate?
oxygen use and basal metabolic rate, cellular metabolism, and growth and development
68
What is the secretion of thyroid hormone controlled by?
the level of iodine in the thyroid gland and by negative feedback systems involving both the hypothalamus and the anterior pituitary gland
69
Calcitonin
lowers the blood level of calcium, secretion is controlled by calcium levels in the blood
70
Where are parathyroid glands?
embedded on the posterior surfaces of the lateral lobes of the thyroid
71
Principal cells
in parathyroid glands; produce parathyroid hormone and oxyphil cells
72
Parathyroid hormone (PTH)
regulates the homeostasis of calcium and phosphate by increasing blood calcium level and decreasing blood phosphate level
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Blood calcium level
directly controls the secretion of calcitonin and parathyroid hormone via negative feedback loops that do not involve the pituitary gland
74
Where are adrenal glands located?
superior to the kidneys
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Three zones of the adrenal cortex
zona glomerulosa, zona fasciculata, and zona reticularis
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Zona glomerulosa
secretes mineralocorticoids
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Zona fasciculata
secretes glucocorticoids
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Zona reticularis
secretes androgens
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Mineralocorticoids (aldosterone)
increase sodium and water reabsorption and decrease potassium reabsorption, helping to regulate sodium and potassium levels in the body
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What controls secretion of mineralocorticoids?
the renin-angiotensin pathway and the blood level of potassium
81
Glucocorticoids (cortisol)
promote the breakdown of proteins, formation of glucose, lipolysis, resistance to stress, anti-inflammatory effects, and depression of the immune response
82
What controls the secretion of glucocorticoids?
it is controlled by CRH (corticotropin-releasing hormone) and ACTH (adrenocorticotropic hormone) from the anterior pituitary
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Androgens secreted by the adrenal cortex usually have ______ _______
minimal effects
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What does the adrenal medulla consist of?
hormone-producing cells called chromaffin cells, which surround large blood-filled sinuses
85
Medullary secretions
epinephrine and norepinephrine which produce effects similar to sympathetic responses
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Epinephrine and Norepinephrine
released under stress by direct innervation from the autonomic nervous system
-help the body resist stress
87
Pancreas
a flattened organ located posterior and slightly inferior to the stomach and can be classified as both an endocrine and exocrine gland
88
Histological components of the Pancreas
pancreatic islets or islets of Langerhans, and clusters of cells
88
Alpha cells
secrete the hormone glucagon which increases blood glucose levels
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Beta cells
secrete the hormone insulin which decreases blood glucose levels
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Delta cells
secrete growth hormone inhibiting hormone or somatostatin, which acts as a paracrine to inhibit the secretion of insulin and glucagonF
90
F-cells
secrete pancreatic polypeptide, which regulates release of pancreatic digestive enzymes
91
How is the regulation of glucagon and insulin secretion?
via negative feedback mechanisms
92
Ovaries
located in the pelvic cavity and produce sex hormones related to the development and maintenance of female sexual characteristics, reproductive cycle, pregnancy, lactation, and normal reproductive functions
93
Female sex hormones
estrogens and progesterone
(inhibin and relaxin)
94
Testes
lie inside the scrotum and produce sex hormones related to the development and maintenance of male sexual characteristics and normal reproductive functions
95
Male sex hormones
testosterone (inhibin)
96
Pineal gland
attached to the root of the third ventricle, inside the brain
97
Histological components of the pineal gland
secretory parenchymal cells called pinealocytes, neuroglia cells, and scattered postganglionic sympathetic fibers
98
Seasonal affective disorder (SAD)
a type of depression that arises during the winter months when day length is short, is thought to be due, in part, to over-production of melatonin.
99
What can relieve seasonal affective disorder?
bright light therapy, repeated doses of several hours exposure to artificial light as bright as sunlight
100
Thymus gland
secretes several hormones related to immunity
101
What promotes the proliferation and maturation of T cells?
thymosin, thymic humoral-factor, and thymopoietin
102
Eicosanoids
act as paracrines and autocrines in most body tissues by altering the production of second messengers, such as cyclic AMP
103
What inhibits a key enzyme in prostaglandin synthesis and are used to treat a wide variety of inflammatory disorders?
aspirin and related nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and acetaminophen
104
Growth factors
hormones that stimulate cell growth and division
105
Examples of growth factors
epidermal growth factor (EGF), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), nerve growth factor (NGF), tumor angiogenesis factors (TAFs), insulinlike growth factor (IFG), and cytokines
106
What happens if a stress is extreme, unusual, or long-lasting?
the normal mechanisms may not be sufficient, triggering a wide-ranging set of bodily changes called the stress response or general adaption syndrome (GAS)
107
Productive stress
eustress
108
Harmful stress
distress
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Stressors
the stimuli that produce the general adaptation syndrome
110
Examples of stressors
any disturbance: heat or cold, surgical operations, poisons, infections, fever, and strong emotional responses
111
Alarm reaction
initiated by nerve impulses from the hypothalamus to the sympathetic division of the ANS and adrenal medulla
112
What is affected by fight-or-flight reactions?
increased circulation, catabolism for energy production, and decrease nonessential activites
113
Resistance reaction
inhibited by regulating hormones secreted by the hypothalamus
114
Resistance reaction regulating hormones
CRH (corticotropin-releasing hormone), GHRH (growth hormone releasing hormone), and TRH (thyrotropin releasing hormone)
115
QCRH
stimulates the adenohypophysis (anterior pituitary) to increase its secretion of ACTH (adrenocorticotropic hormone), which in turn stimulates the adrenal cortex to secrete hormones
116
Resistance reactions are...
long-term and accelerate catabolism to provide energy to counteract stress
117
Glucocorticoids
produced in high concentration during stress
-create distinct physiological effects
118
Results from exhaustion
results from dramatic changes during alarm and resistance reactions
119
What causes exhaustion?
loss of potassium, depletion of adrenal glucocorticoids, and weakened organs
120
Stress-related conditions
gastritis, ulcerative colitis, irritable bowel syndrome, peptic ulcers, hypertension, asthma, rheumatoid arthritis, migraine headaches, anxiety, and depression
121
People under stress are at a greater risk of?
developing chronic disease or of dying prematurely
122
Link between stress and immunity
interleukin-1 (IL-1) produced by macrophages; it stimulated secretion of ACTH
123
Two different regions of the ectoderm the pituitary gland originates from
1. the anterior pituitary derives from the neurohypophyseal bud, located on the floor of the hypothalamus
2. the anterior pituitary is derived from an outgrowth of ectoderm from the mouth called the hypophyseal pouch
124
The thyroid gland develops as...
a midventral outgrowth of ectoderm, called the thyroid diverticulum, from the floor of the pharynx at the level of the second pair of pharyngeal pouches
125
Parathyroid glands develop from...
endoderm as outgrowths from the third and fourth pharyngeal pouches
126
The adrenal cortex is derived from...
intermediate mesoderm from the same region that produces the gonads
127
The adrenal medulla derives from..
the neural crest
128
The pancreas develops from...
the outgrowth of endoderm from the part of the foregut that later becomes the duodenum
129
The pineal gland arises as...
an outgrowth between the thalamus and colliculi from endoderm associated with the diencephalon
130
The thymus gland arises from...
endoderm of the third pharyngeal pouch
131
Aging and pituitary gland
production of hGH decreases with age,
production of gonadotropins and of TSH increases with age,
-ACTH levels unchanged with age
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Aging and thyroid gland
decreases output of thyroxin with age
133
Aging and thymus gland
begins to atrophy at puberty,
adrenal glands produce less cortisol and aldosterone with age
134
Aging and the pancreas
releases insulin more slowly with age, and receptor sensitivity to glucose declines
135
Aging and the ovaries
reduce in size and no longer respond to gonadotropins
136
Pituitary gland disorders
pituitary dwarfism, giantism, and acromegaly
-hyposecretion of hGH
-hypersecretion of hGH during childhood results in giantism and during adulthood results in acromegaly
136
Diabetes insipidus
disorder associated with dysfunction of the posterior pituitary
-hyposecretion of ADH causes excretion of large amounts of dilute urine and subsequent dehydration and thirst
137
Thyroid gland disorders
cretinism, myxedema, Grave's disease, goiter
138
Cretinism
hyposecretion of thyroid hormones during fetal life or infancy
139
Myxedema
hypothyroidism during adult years
140
Grave's disease
most common form of hyperthyroidism, an autoimmune disease
141
Goiter
an enlarged thyroid gland
142
Hypoparathyroidism
results in muscle tetany
143
Hyperparathyroidism
produces osteitis fibrosa cystica
144
Adrenal gland disorders
cushing's syndrome, addison's disease benign tumords A
145
Cushing's syndrome
results from a hypersecretion of cortisol by the adrenal cortex
146
Addison's disease
hyposecretion of glucocorticoids
147
Diabetes Mellitus
a group of disorders causes by an inability to produce or use insulin
148
Type I Diabetes
insulin-dependent diabetes mellitus is caused by an absolute deficiency of insulin
149
Type II Diabetes
insulin-independent diabetes is caused by a down-regulation of insulin receptors
150
Hyperinsulinism
results when too much insulin is present and causes hypoglycemia and possibly insulin shock
